Electroceramic elements are known in which the specific resistance of the ceramic body has a negative temperature coefficient, and which therefore are usable as NTC resistors. These ceramics exhibit decreasing electrical resistance with increasing temperature. The resistance values of NTC materials show an approximately exponential dependency. The sensitivity of the change in resistance is a factor of the temperature indicating a B value. The greater this B value is, the greater the temperature sensitivity of the specific resistance of the ceramic.
Conventional NTC ceramic elements are made up of a ceramic body, onto which contact layers have been applied. Since standards are prescribed for these ceramic elements that specify the size of these elements, only one resistance value can be realized with a component of a prescribed standard having a particular resistance temperature characteristic profile (B value) and a particular capacitance. In addition, a passivation layer can be applied to these components, which protect the component against external influences, for example a change in resistance when the component is soldered.
In U.S. Pat. No. 5,245,309, ceramic NTC elements are disclosed, in which a ceramic body is produced using multi-layer technology and is made up of ceramic layers with internal electrodes arranged in them. These internal electrodes each contact an external contact layer and form an electrode terminal. Furthermore, an external passivation layer, such as glass, may be applied to the surface of the elements.
With this technology, it is possible to realize different resistances by varying the arrangement of the internal electrodes in components having the same component standard. However the electrical property, the B value, which is also important for the NTC materials, cannot be changed using this technology.
But to use the NTC elements for specific tasks, such as monitoring the temperature in mobile telephones, ceramic elements are desired which exhibit electrical properties matched to the particular problem area, in particular matched capacitance, a matched resistance/temperature characteristic profile (B value) and matched resistances at a given temperature. Since strict component standards frequently need to be maintained, there is a need for components that have different electrical properties but that have electroceramic bodies with the same dimensions and contact layers with the same dimensions. With conventional NTC elements, as described above, the B values and the resistance values cannot be varied simultaneously at will.